Some pieces of agricultural equipment known in the art as forage harvesters and combine harvesters are used to collect and process crop material from a field. Generally, such agricultural harvesting machines are equipped with crop material cutting and/or collecting devices, such as maize, corn or grain cutting headers or pick-up units for picking up e.g. hay, grass or straw off the ground. In addition to such initial gathering operations, the machines are also provided with second-stage gathering means for transferring crop material and include intake elements for taking in harvested/gathered crop material and feeding it to further crop processing means of the harvesting machine.
In a forage harvester, for example, the intake elements usually comprise a set of feedrolls which take in harvested crop material and feed it to a cutterhead, which is part of the further crop processing means. The rotating cutterhead co-operates with a fixed shear bar, operable to chop up the crop material fed thereto by the feedrolls. With grass-like materials which are kernel-free it is sufficient to slit the crop material, e.g. the stems of the plants are cut to length using a cutterhead such as a rotary knife drum. When cutting maize, the cobs may be slit into smaller size by the cutterhead, and it is preferred if the majority of the kernels are broken or cracked, which is needed in order to facilitate the complete digestion of the crop material, including the maize kernels, by farm animals. Therefore a compressor roll assembly, a set of closely adjacent, co-operating compressor rolls with fluted surfaces, may be provided for cracking the chopped crop material. The comminuted/processed crop material is then propelled by a blower or accelerator out of the harvester through a spout, directing the material flow into a temporary container moved behind or aside the forage harvester, before being stored and eventually being foddered to livestock.
In a combine harvester, for example, the intake elements generally comprise a straw elevator, which feeds the crop material to the crop processing means comprising threshing means, including one or more threshing drums, further separation means, such as straw walkers, and cleaning means, including sieves and a ventilator, operable to remove impurities such as chaff and pieces of straw from the grain kernels.
In use, in order to harvest crop material, an agricultural harvesting machine is provided at its front side with a front attachment comprising a first gathering element for gathering crop material and feeding it in a direction opposite to the direction of motion of the forage harvester, and a second gathering element for transferring crop in a direction transverse to the direction of motion towards an intake mouth of the forage harvester. The first gathering element may be a crop material cutting and/or collecting device, such as for example a row dependent cutting means as known in the art, a row independent cutting means as described in EP-0 860 106, or a windrow pick-up device. The second gathering element is the transferring means for transferring the gathered crop material to an intake mouth of the harvesting machine, the intake mouth generally being of a smaller width than the second gathering element. The intake mouth is generally smaller width than the width of the first gathering element so the gathered crop must be brought more towards the longitudinal axis of the machine. The second gathering element may be, for example, an auger or a combination of vertical take-over drums as described in EP-0 860 106. The first gathering element collects and/or picks up crop material, and the second gathering element conveys the crop material to the intake mouth at the front part of the forage harvester.
The length to which crop material is cut depends on the conveyance speed of the feedrolls and on the speed of the cutterhead.
Generally on current forage harvesters the relationship between the speed of the second gathering element and the speed of the intake elements is not fixed since there is no fixed connection between each other. In most cases, the operator has to change the speed of the second gathering element by changing sprockets or gears whenever he/she chooses another speed of the intake elements. The right relationship between the speed of the second gathering element and the speed of the intake elements is very important for efficient feeding/crop throughput, good machine capacity and good quality of chop, especially in the case of a forage harvester. Since the front attachment and intake elements are generally not connected to each other on the current machines, the right relation can sometimes only be approximated.
U.S. Pat. No. 3,945,175 describes a feedroll drive mechanism for forage harvesters wherein a hydrostatic transmission is used to vary the length of cut of crops processed by the chopping mechanism. The hydrostatic transmission drives both the feedroll mechanism and the forwardly located gathering mechanism of the harvesting unit, such that the relative speeds of the crop gathering unit and the feedrolls remain unchanged.
Generally, the first gathering element (like the reel on a pickup and the chains and rotors on corn-leaders) and the second gathering element are driven by the same header attachment input shaft. Connecting this input shaft to the feedroll drive as in U.S. Pat. No. 3,945,175 makes the speed of the second gathering element and also the speed of the first gathering element vary together with the feedrolls.
With a forage harvester, when crop material is fed to the feedrolls at a too high speed (speed of the second gathering element higher than the speed of the feedrolls), a plug of material is formed in front of the feedrolls, which hampers the crop flow and causes material to be unevenly cut. If the speed of the second gathering element is lower than the speed of the feedrolls, material may be grasped by the feedrolls and torn apart. Here again, an irregular length of cut is obtained at the cutterhead, while in both cases a stationary length of cut is desired. Also when picking up e.g. hay, grass or straw, problems can be caused due to the speed of the second gathering element compared to the speed of the feedrolls: if the speed of the second gathering element is too low, material will pass below it and will be lost; if the speed of the second gathering element is too high, hay will be pushed forward. Here again, an irregular length of cut will be obtained.
In U.S. Pat. No. 4,044,557 an arrangement is disclosed in which feed-rolls are provided with an automatic speed control that increases the speed of the rollers when they are moved apart by humps of crop material in order to rid themselves of larger than normal slugs. Separate hydraulic pumps are provided for driving the feed-rolls and a standing crop cutter, although in each embodiment the two pumps are operably connected to each other between their respective control levers by a lost motion linkage. Although their control levers are not necessarily swung uniformly, they are coupled and are swung in unison.
It is an object of the present invention to provide improved agricultural machinery. It is a further object of the present invention to provide improved front/header attachments for agricultural machines, and improved arrangements and methods for operating the same.